NXT.......rubbish??....THINK AGAIN!

FullRangeMan · « **Reply #300 on:** 30 Oct 2009, 02:20 am »

Sorry to know this. Hope the Visaton exciter can do a better performance if you will use it.
I also believe in the NXT tech as a fullrange no Xover, no EQ, hi-end speaker.

j gale · « **Reply #301 on:** 30 Oct 2009, 03:46 am »

Zygadr, Your last post seems to be an overreaction to some perceived problems. Sound is too good to just give up on. Exciters have not failed have they? I have had a foot come off of one and simply glued it back on with no further problems. I don't think high volume is a problem either. Worry about the exciters if and when they actually fail. The high frequency roll off I don't really hear. When I play high frequency bells cymbals etc. or high frequency percussive sounds I find it satisfying without hiss or sizzle.(to hell with the measurements) I don't hear anything missing on the high end. Rather it sounds natural to me. I probably have some high eff. reflection from the window behind my panels. Better exciters and panel material will come along. I see that Elac uses a honeycomb panel with paper faces. I have some white gatorfoam on order since it is different than the black. This is the beginning NOT the end. Jim

usp1 · « **Reply #302 on:** 30 Oct 2009, 04:32 am »

Zygadr,

Don't give up yet. We are getting some negative results particularly with the rolled off highs and lows but what ever is coming through is very nice...very transparent and clear.

I spent some time listening to my panels (currently mismatched because one has 7 exciters the other 5).They are white gatorfoam 2'x4' with temporary tape not the 3M tape. I finally figured out that some of the rattle was due to loose footers on two of the exciters. It is much reduced now and only happens when I really push the volume. The SPL levels can get quite high but that requires serious amp power. My 200 wpc emo has no problem driving the panels to ridiculous levels (probably unsafe levels for the exciters).

Do we think it was a waste of money? Absolutely not. I think we all got very excited because this was such an easy project and relatively cheap. It is a bit disappointing that we are not able to get the real highs but that may still happen as others explore other materials. (The nomex panels are tempting 2'X3' for about $72 with fibreglass facing. Not sure how that would sound but something to think about.)

So don't bail out yet. This is still a work in progress and your experience with this technology is invaluable for all of us.

Donka · « **Reply #303 on:** 30 Oct 2009, 04:57 am »

Zygadr,

Hang in there brother, I am having fun with this project and didn't expect it to be perfect out of the gate, I surely don't blame you for anything. The more information we get, it looks like it is just the nature of the beast were dealing with here.

J Gale is right, the Elac panel material is listed as a paper honeycomb, which I found at least 2 OEM's listed as using for their panels when digging for information. Personally I imagine this would be the cheapest of all honeycomb options but so far have been unable to source some locally. One supplier I use carries aluminum honeycomb with aluminum skins, however it's $27/sqft. I am wondering what the thickness of the Podium and Elac panel material is??

The promising Elac exciter is the 83048 which has a 70% increase in excursion over the 83005. Based on their info, it looks like the sensitivity is up there, and placed correctly gives good dB gain when adding additional exciters. However the one thing I missed when I read their site before, is that they state the gain becomes more lopsided with additional exciters over 2, and then requires frequency response correction. Also they explicitly state they are good to 100Hz and recommend a subwoofer, so if you want to go full range they probably won't do the trick either, though definitely look more stout then the el cheapo's.

J Gale,

I found that when I placed the test panels in the other room for testing, with plaster walls and floor to ceiling glass on one-side that the necessary EQ in the HF decreased by roughly 5dB, it made a large improvement for sure. I believe the HF is traveling through the back sheet quite well, it is just not transferring to the face sheet. I look forward to hearing your results with the white Gatorboard.

I did purchase some 1' x 2' thin aluminum sheet, stainless, and also some extruded acrylic to test. I am wondering what the result would be of using thin plastic film (the type used in vacuum forming) attached to a frame, then using a heat gun to shrink it taught, almost like a drum head.

j gale · « **Reply #304 on:** 30 Oct 2009, 05:38 am »

Donka I would like to get my hands on some honeycomb paper panel. It seems obvious that transfer from back to front surface would be better than with a foam core. Presumably improving treble. That also opens up the possibility of modifying the panel surface in the same way that paper cones are treated with damar, lacquer sprays, mod podge etc. The surface could be stiffened with very little weight being added. Who knows to what effect? Enable patterns may also have quite an effect as claimed in connection with other panels. I have heard a difference from various fullrange drivers.

mkstat · « **Reply #305 on:** 30 Oct 2009, 03:54 pm »

usp1 · « **Reply #306 on:** 30 Oct 2009, 08:30 pm »

Quote from: mkstat on 30 Oct 2009, 03:54 pm

With using more than one exciter we are actually using equalisation - for low frequencies we are summing with better efficency (+6dB per doubling of the exciters/ coherent summing) and for the HF with less (+3dB not coherent summing). If useing more than one exciter full range, there might be some destructive interferences for the high frequencies - less hf output.
Due to the dipole radiation at a certain frequency (depending on the size of the panel) a LF drop (-6dB/oct.) starts.
I like your puristic attitude of no filtering just making the thing as straight as possible by the physical arrangement - it's just a question of point of view and finding the right compromises, but I have the strange feeling that running all exciters full range will keep us running in trouble.

Marcus - Please help me understand this. Would a solution to this be to run some of the exciters with a HP filter. Or would it be to create separate panels one running with only HF the other with lower frequencies? Of course that means a crossover and that destroys the purity of the approach.

mkstat · « **Reply #307 on:** 30 Oct 2009, 10:21 pm »

mkstat · « **Reply #308 on:** 31 Oct 2009, 01:27 am »

j gale · « **Reply #309 on:** 31 Oct 2009, 02:59 am »

It's my understanding that our panels are bipole not dipole and so a different ball game re cancellation etc.

el`Ol · « **Reply #310 on:** 31 Oct 2009, 09:04 am »

Quote from: zygadr on 30 Oct 2009, 06:11 am

So, we need to find out exactly what this ''HARDWAX OIL'' is exactly........brand names, equivalents etc.?

If Balsa wood could be joined to make large sheets and dampened/coated it would make a very interesting material.............maybe ideal?

There is an importer for hardwax oil in Australia (this stuff seems to be a german specialty).
http://www.whittlewaxes.com.au/Home/Home.asp
Hardwax oil contains carnauba wax, according to Wikipedia the hardest natural wax. It comes from Brazil, same as balsa, so pure canauba might be the alternative for the Fullrangeman, if he can?t get the blend over there.

mkstat · « **Reply #311 on:** 31 Oct 2009, 12:02 pm »

j gale · « **Reply #312 on:** 31 Oct 2009, 12:50 pm »

Take a look at NXT explanation --link in post 366

mkstat · « **Reply #313 on:** 31 Oct 2009, 01:09 pm »

mkstat · « **Reply #314 on:** 31 Oct 2009, 01:21 pm »

FullRangeMan · « **Reply #315 on:** 31 Oct 2009, 04:31 pm »

Quote from: el`Ol on 31 Oct 2009, 09:04 am

There is an importer for hardwax oil in Australia (this stuff seems to be a german specialty).
http://www.whittlewaxes.com.au/Home/Home.asp
Hardwax oil contains carnauba wax, according to Wikipedia the hardest natural wax. It comes from Brazil, same as balsa, so pure canauba might be the alternative for the Fullrangeman, if he can?t get the blend over there.

Hi Boys, nice to see Zygard and others running this thread again.
About the Carnauba wax, some 15-20years ago it was used in automotive shining wax (before silicone take the market), and to corrosion prevent spray under the car, but at a time it was no more used under the cars cause it resected the rubbers parts(it made the rubbers dry).
So looks carnauba wax is good to metalic car parts only, in GatorFoam I do not know what it could do, maybe to spray in paper it is OK.

About the sound spread pattern of a NXT panel, as Zygard, others and NXT-UK inform on some papers it is Bipolar(with just a single panel-driver) and Omnipolar. But it do not have two drivers(one firing front and other firing back) it is Bipolar because it do not the the Negative phase sound firing back, as a cone speaker, and do not have the OB self cancelation effect under 500Hz. But we all know this, Iam repetitive.
Cheers

P.S.: Just remember, Carnauba oil is very used yet today to spray or rub in real wood forniture, but it is a magnet to termites. There is others tree oils, as Cedar, Pine etc

P.P.S.: I will not buy exciters and panels this year. Iam waiting some honeycomb material and a super exciter, I have no garage to test procedures.

P.P.P.S.: Errata: Sorry, Carnuba oil was not used under the car, just to shining the paint, it was Mamona oil that was used under the car and damage the rubbers, so Carnauba oil seems a inert tree oil, maybe good to synthetic panels spray made of paper.

el`Ol · « **Reply #316 on:** 31 Oct 2009, 05:44 pm »

Quote from: FULLRANGEMAN on 31 Oct 2009, 04:31 pm

P.P.S.: I will not buy exciters and panels this year. Iam waiting some honeycomb material and a super exciter, I have no garage to test procedures.

Seems there is a new honeycomb candidate, and the manufacturer claims it's inexpensive:
http://www.diyaudio.com/forums/planars-exotics/133711-piezo-nxt-type-panel-42.html
But I wouldn't underestimate mother nature. The balsawood doesn't only sound neutral, when I measured the force / excursion curve of a balsa stripe I couldn't find non-linearities at low excursions. The problem is really just the low damping. Pure carnauba could be applied with heat instead of solvent, maybe an advantage.
But the problem with the termites, could be an argument in tropical countries.

mkstat · « **Reply #317 on:** 31 Oct 2009, 05:49 pm »

mkstat · « **Reply #318 on:** 31 Oct 2009, 06:03 pm »

Russell Dawkins · « **Reply #319 on:** 31 Oct 2009, 06:19 pm »

Quote from: mkstat on 31 Oct 2009, 12:02 pm

Quote from: j gale on 31 Oct 2009, 02:59 am
It's my understanding that our panels are bipole not dipole and so a different ball game re cancellation etc.

I'm afraid this is not correct.
In a bipole system, two drivers fire in phase with one another, but in opposite directions.

This is not possible with one panel unless it's expanding and contracting in thickness according to the input signal.
Well in fact the panel does contract and expand to some extend - but not in a way so that bipolar behavior is the result.

... anyone with a good understanding of the basics of acoustics would realize that mkstat is absolutely correct on this point.

It is when the discussion became argumentative on this fundamental notion that I bailed on this thread months ago. To think a panel could exhibit bipolar or omnipolar radiation in bass frequencies is to demonstrate that science is not supporting proceedings, to put it politely.
To be less polite - this is fantasy, and not helping with any potential understanding.

It appears that the chaotic nature of the behavior of the panel is not a detriment to mid and high frequency performance, but even if the wish is not to use any form of crossover through this range, I think it will be found to be essential to use a sub, and crossed fairly high, to get decent power handling out of this design. Then, to save the exciters from the effects of over extension, a high pass filter to the mid-high panels will be found necessary.